Process for the manufacture of aliphatic primary amines



Sept. 1, 1936. H. M. GUlNoT PROCESS FOR THE MANUFACTURE OF' ALIPHATIC PRIMARY AMINES Patented Sept. I, 1936l UNITED STATES sassari PaocEss Foa 'rnE mancuernas or' am Amma Heim Mmm om, mim, peux-sms.

France, assigner. to

France, a corporation of France Usines De Melle, MelleI Application February 21, 1936, Serial No. 65,122

In France February 18. 1935 12 Claim!- This invention relates to the manufacture of aliphatic primary amines. y

Numerous publications have dealt'l with the possibility of producing aliphatic or aromatic primary amines by the action of the 'alcohols upon ammonia-in the presence of hydrogenation catalysts, particularly nickel, in the liquid or vapour phase and with or without pressure.

It is, however, to be noted that the various publications relating to this question present very apparentv contradictions, more especially in connection with working in the vapour phase.

Thus, in French patent specification No. 669,824 it is proposed to produce butylamine by the interaction of ammonia gas and butyl alcohol at 300 C. with nickel as catalyst. According to French patent specification No. 687,398 one should obtain a mixture of the three butylamines by working with a similar catalyst at 250 C.

Now, according to Komatsu's work (Mem. Coll. Kioto 8A--241), by working under those conditions, one would obtain only the nitrile with the evolution of hydrogen and, at 300 C., the cocincient of conversion would be of the order of I0 to per cent. on a single passage. From 180 C. onwards, the evolution of hydrogen is abundant. These latter results would, moreover. appear to have been confirmed by the work of Maihle and Godon (Bull. 21-1917--p. 278), according to which the amines would be totally dehydrogenated.. with the ,formation of the corresponding nitriles, by the passage over reduced nickel at 320 C.

The aforesaid French patent speciiication No. 687,398 also indicates the possibility of converting into butylamine, in a single passage, up to 80% of the butyl alcohol used, 4by employing copper at 210 C. as catalyst. Now, by way of contradiction, one may read in the paper by M. Guyot (Bull. Societe Chimique-1930-p.' 209) as followsz In the gaseous phase the productionA of amines is rather small, and it is preferable to work in the liquid phase when one is not limited by excessive pressures. Y

Finally', in some publications, the authors appear to make no distinction between the yields proper and the coefcients of conversion obtained on each passage over the catalyst; this again adds to the confusion.

However that may be, when the study of the action, in the gaseous phase, of ammonia gas on the alcohols in the presence of an hydrogenation catalyst is taken in its entirety, it is easy to veriiy' the correctness of Komatsus work, accord- (Cl. ZBO-127) ing to which, under certain conditions of temperature, there is observed an intense absorption of ammoniagas without any appreciable production` o! amines but', on the contrary, with an abundant' production of nitrile and a corresponding evolution o1 hydrogen, in accordance with the equation It ismoreover, correct that, on working at l0 temperatures that are not so high as those indicated by Komatsu, amines are, in fact, obtained but the coemclents of conversion are very small for each passage over the catalyst; by way of compensation, the true yields--L e. the quan- 15 tity of amines formed in proportion to the alcohol and to the ammonia that have disappeared in the reaction-are excellent. l

If now ,the temperature is increased with a view to improving the coefilcients of conversion and 20 obtaining an economical working, it is observed that, very soon, the production of the nitriles increases and rapidly becomes preponderant;-one ultimately rlnds oneself faced by two alternatives-i. e. f 25 (l) That of having a low coemcient of conversion on every -r= :f e over the catalyst but a good yield as compared with the initial materials that have disappeared in the reaction, or

(2) That of having a high coemcient of con- 30 version'butv being led to a deiiclent amine yield.

-It is also to be noted that numerous catalysts produce-when the temperature increases, for example, from between ,220 and 230 C. for nickel-the destruction of a part of the alcohol 35 employed, with conversion into the corresponding saturated hydrocarbon; this diminishes the ilnal -yield correspondingly.

The present invention has as its subject matter a.v process comprising a set of arrangements o which enable a complete yield of primary amines to' be obtained froma given alcohol whilst ensuring a high percentage of conversion on each passage over the catalyst or catalysts employed, so that, in short, an economical working is obtained. The process consists essentially in effecting, in a ilrst stage, the partial conversion of the alcohol into nitrile and then. in a second stage, partially hydrogenating the nitrile thus formed. The product obtained is then treated for the separation of the primary amine, which is collected. and the residual mixture is separated on the one hand into nitrile which is preferably returned to the hydrogenation stage and, on the other .55

hand, into a mixture of the unconverted alcohol and secondary and tertiary amines which is caused to re-enter the circuit along with the alcohol that is supplied thereto.

The following description considered in con- Junction with the accompanying drawing will enable the mechanism of the invention to be well understood:-

The alcohol to be treated passes from a tank I into a catalyst furnace 2 at the same time as a large excess of ammonia gas which is forced into the furnace 2 by a fan 3. The furnace 2 is charged with a dehydrogenation catalyst that is heated to a temperature sufficiently high for converting a large fraction of the supplied alcohol into nitrile with a corresponding production of pure hydrogen.

The gases and vapours leaving the furnace 2 are cooled in a cooler 4, so as to lower their temperature suitably, and they are then passed into a second catalyst furnace 5 provided with an hydrogenation catalyst. Owing to the action of the catalyst, to the adequate temperature prevailing in the furnace 2 and to the large excess of hydrogen contained in the gases flowing from the furnace 2, the nitrile is effectively hydrogenated into corresponding amines.

The gases and vapours leaving the catalyst furnace 5 then pass into a. cooler 6 where a partial condensation is produced, whilst the excess of ammonia gas and hydrogen saturated by the vapours of the condensed liquid collected in a receptacle 1 is forced continuously into the furnace 2 by the fan 3. At the same time, the necessary quantity of ammonia gas is supplied continuously through a pipe 8.

The product condensed in the vessel 1 is composed of primary, secondary and tertiary amines, also a certain quantity of unconverted alcohol as well as of a good quantity of nitrile and, naturally, of the water formed in the reaction. It is forced by a pump through conduit 1a into a tank 8 from which it flows through conduit 9a into a column Ill where it is freed from the dissolved ammonia gas which is passed back into the circuit through conduit lI0a. The liquid product freed from ammonia gas is then passed into a distillation column Il where the primary amine, which has the lowest boiling point of the three amines, is then easily separated by being drawn oif at the top of the column Il through a pipe I2 to a. condenser |2a. The condensed primary amine may then be Withdrawn from the latter through conduit I2b and led to any suitable collector receptacle or the like or it may be recirculated, to any desired extent, through conduit I2c.

On the other hand, the nitrile and the alcohol, the boiling points of which are nearly identical, can only be separated by using the property, possessed by the nitriles, of giving with water a mixture which has a ilxed composition and the boiling point of which is lower than that of the azeotropic mixture formed between water and the alcohol. Thus, after separation of the primary amine at the top of the column Il, the residual mixture is passed into a column I3 at the top of which there is obtained the water-nitrile mixture of minimum boiling point, which mixture, after condensation in condenser lla to which it is withdrawn through pipe |322, separates generally into two layers.

The nitrile may, without disadvantage, contain a certain proportion of alcohol; after decantation in vessel Il. the nitrile is returned into the hydrogenation circuit at Il in front of the hydrogenation furnace l. The aqueous layer can be returned to the circuit at any suitable point. The condensate in condenser Ila may be recirculated, to any desired extent, through conduit lib.

The water, which is formed in the course of the reaction and which may be4 present in the initial material (alcohol) is generally sufficient for carrying on' all the nitrile in the form oi' an azeotrpic mixture. In any case, it is easy, owing to the reflux at the top of column I3, to keep in this column a quantity of water suflicient to ensure the complete carrying of! of the nitrile in all cases. The distillation is regulated in conventional manner so that all the nitrile is removed at the same time as all the water, so that the mixture of alcohol and secondary and tertiary amines flowing away at the base will be anhydrous.

The column Il enables not `only the nitrile to be separated but also the dehydration of the mixture to be effected precisely through the intermediary of the azeotropic water-nitrile mixture.

If the latter cannot be decanted, as in the case of aceto-nitrile for example, it is possible to remove the water therefrom by treatment by means of a concentrated aqueous solution of a salt, for example, a solution of potassium carbonate.

Be that as it may, an anhydrous mixture of alcohol and secondary and tertiary amines is obtained at the base of the column Il. Now, it has been foundand this is one of the features of the present invention-that these amines could be reconverted quantitatively into nitrile by the action of ammonia by working precisely under the reaction conditions of the furnace 2. It is therefore recommended to pass the mixture or alcohol and amines, withdrawn at the base of the column I3, back through conduit |3c into the general circuit in front of the furnace that catalyses to nitrile-i. e. back into the tank containing the supply of fresh alcohol. However, the scope of the present invention is not departed from by causing the recovered products to reenter the circuit at any suitable point.

Suitable conventional vents or relief passages, communicating with the atmosphere, may be provided where deemed desirable, as indicated for example at l1;

Once the apparatus has attained equilibrium after the first few hours of working, it is observed that no gas leaves the apparatus. Only ammonia gas and alcohol enter and only primary amine leaves with a quantitative yield because there is no formation of hydrocarbons.

It is possible to work at a pressure that differs from the atmospheric pressure for the purpose of still further increasing the elllcacy of the work; for example, it is possible for the fan to be so placed as to create a slight diminution of pressure in the dehydrogenation furnace and a slight increase of pressure in the hydrogenation furnace.

'I'he scope of the invention is not departed from by conducting the operation of dehydrogenation at such a temperature that a small quantity of aminesis formed at the same time as the nitrile.

Example I Butyl alcohol (B. P. 117 C.) is introduced at a speed of 10 kilogrammes per hour into the catalyst furnace 2 that is filled with a catalyst consisting of reduced nickel (whether on a carrier or not) maintained at a temperature of 300 C. 'I'he fan 3 furnishes a supply of gas at a speed of about 30 cubic metres per hour, this gas consisting of about 75% of ammonia. The catalyst in the furnace ,I likewise consists of nickel, but this nickel is maintained at the temperature of 90 to 100 C.

Monobutylamme (B. P. '18 cra withdrawn at, At the top of the the top of the column II. column I3, there is shown a temperature of 88 C. corresponding to the minimum boiling point mixture water-butyronitrile. This mixture is passed to condenser I3a and thence to decanter I4.

, The top layer that is separated in the decanter I4 consists of butyronitrile containing a little water and butyl alcohol, and,l returns into the hydrogenation circuit at the point II in front of the furnace 5. The aqueous layer withdrawn from decanter I4 is treated in a small auxiliary column I6 for the purpose of removing from it the small quantity of butyronitriie and alcohol which it contains in solution and which is passed back to the condenser I3a. of the column I i. Pure water ilows away from the base of the column I6.

An anhydrous mixture of butyl alcohol, dibutylamine and tributylamine is obtained at the base of the column I3. This mixture is passed back into .the tank I to mix with the supply of fresh butyl alcohol.

On each passage, 60 per cent. of the butyl alcohol is converted into monobutylamine with a quantitative yield, because there is no formation of hydrocarbons or of accessory products, the dibutylamine and the tributylamine being continuously reconverted into nitrile in the furnace 2, as has herelnbefore been explained.

Example I1 In the same apparatus as that used in Example I, reduced copper is placed in the dehydrogenation furnace 2 and reduced nickel is placed in the hydrogenation'furnace 5. The furnaces being heated at 360 C. and 90 C. respectively, a quantitative conversion of the butyl alcohol into butylamine is obtained.

Example 11i Ethyl alcohol can be converted into monoethylamine by charging the two furnaces with reduced copper, the temperature at which the first furnace is heated being 340 C. and that at which the second is heated being 170 C.

These examples are not limitative.

What I claim isz- 1. Process for the manufacture of a primary lower alkyl mono amine by reacting a primary lower aliphatic monohydric alcohol containing more than one carbon atom per molecule with ammonia, comprising essentially first transforming the alcohol partially into nitrile by dehydrogenation in the vapor phase in a first dehydrogenation stage in presence of a dehydrogenation catalyst, employing an excess of ammonia over that theoretically necessary for conversion of the alcohol into nitrile, and then subjecting the resultant mixture of nitrile and hydrogen to hydrogenation in the vapor phase in a second subsequent hydrogenation stage in the presence of a hydrogenation catalyst.

2. Process for the manufacture of a primary lower alkyl mono amine by reacting a primary lower aliphatic monohydric alcohol containing more than one carbon atom per molecule with ammonia, comprising essentially first transforming the alcohol partially into nitrile by dehydrogenation in the vapor phase in a first dehydrogenation stage in presence of a dehydrogenation catalyst. employing an excess of ammonia over that theoretically necessary vfor conversion of the alcohol into nitrile, then subjecting the resultant mixture of nitrile and hydrogen to hydrogenation in the vapor phase in a second subsequent hydrogenation stage in the presence of a hydrogenation catalyst, subjecting the products of the hydrogenation to condensation, and returning the uncondensed fraction to the dehydrogenation stage.-

3. Process for the manufacture of a primary lower alkyl mono amine by reacting a primary lower aliphatic monohydric alcohol containing more than onel carbon atom per molecule with ammonia, comprising essentially first transforming the alcohol partially into nitrile by dehydrogenation in the vapor phase in a first hydrogenation stage in presence of a dehydrogenation catalyst, employing an excess of ammonia over that theoretically necessary for conversion of the alcohol into nitrile, then subjecting the resultant mixture of nitrile and hydrogen to hydrogenation in the vapor phase vin a second subsequent hydrogenation stage in the presence of a hydrogenation catalyst, removing dissolved ammonia from the resultant amine-containing product, submitting the remaining liquid to distillation, and drawing oi the amine as head product.

4. Process for the manufacture of a primary lower alkyl mono amine by reacting a primary lower aliphatic monohydric alcohol containing more than one carbon atom per molecule with ammonia, comprising essentially rst transforming the alcohol partially into nitrile by dehydrogenation in the vapor phase in a first dehydrogenation stage in presence'of a dehydrogenation catalyst, employing an excess of ammonia over that theoretically necessary for conversion of the alcohol into nitrile, then subjecting the resultant mixture of nitrile andv hydrogen to hydrogenation in the vapor phase in a second subsequent hydrogenation stage in the presence of a hydrogenation catalyst, removing dissolved ammonia from the resultant amine-containing product, submitting the remaining liquid' to distillation, drawing off the amine as head product, recovering the unchanged nitrile from the residual mixture and returning it to the hydrogenation stage.

lower alkyl mono amine by reacting a primary lower aliphatic monohydric alcohol containing more than one carbon atom per molecule with ammonia, comprising essentially first transforming the alcohol partially into nitrile by dehydrogenation in the vapor phase in a first dehydrogenation stage in presence of a dehydrogenation catalyst, employing an excess of ammonia over that theoretically necessary forconversion of the alcohol into nitrile, then subjecting the resultant mixture of nitrile and hydrogen to hydrogenation in the vapor phase in a second subsequent hydrogenation stage in the presence of a hydrogenation catalyst, removing dissolved. ammonia from the resultant amine-containing product, submitting the remaining liquid to distillation, drawing oi the amine as head product, and separating the residual mixture into nitrile for return to the hydrogenation stage and into a mixture of secondary and tertiary amines and unconverted alcohol for return to the dehydrogenation stage.

6. Process for the manufacture of a primary lower alkyl mono amine by reacting a primary lower alphatic monohydric alcohol containing mitting the remaining liquid to distillation, drawing off the amine as head product; and extractlng the nitrile from the residual mixture as a nitrile-water mixture of constant composition for return to the hydrogenation stage.

7. Process for the manufacture of a primary lower alkyl mono amine by reacting a primary lower aliphatic monohydric alcohol containing more than one carbon atom per molecule with ammonia, comprising essentially first transforming the alcohol partially into nitrile by dehydro-` genation in the vapor phase in a first dehydrogenation stage in presence of a dehydrogenation catalyst, employing an excess of ammonia over that theoretically necessary for conversion of the alcohol into nitrile, then subjecting the resultant mixture of nitrile and hydrogen to hydrogenation in the vapor phase in a second subsequent hydrogenation stage in the presence of a hydrogenation catalyst, removing dissolved ammonia from the resultant amine-containing product, submitting the remaining liquid to distillation, drawing off the amine as head product, extracting the nitrile from the residual mixture as a nitrile-water mixture of constant composition, dehydrating the nitrile, and returning it to the hydrogenation stage.

8. Process for the manufacture of a primary lower alkyl mono amine by reacting a primary lower aliphatic monohydric alcohol containing more than one carbon atom per molecule with ammonia, comprising essentially first transforming the alcohol partially into nitrile by dehydrogenation in the vapor phase in a rst dehydrogenation stage in presence of a dehydrogenation catalyst, employing an excess of ammonia over that theoretically necessary for conversion of the alcohol into nitrile, then subjecting the resultant mixture of nitrile and hydrogen to hydrogenation in the vapor phase in a second subsequent hydrogenation stage in the presence of a hydrogenation catalyst, removing dissolved ammonia from the resultant amine-containing product, submitting the remaining liquid to distillation, drawing off the amine as head product, extracting the nitrile from the residual mixture as a nitrile-water vapor mixture of constant composition, condensing same, decanting the nitrile, returning the latter to the hydrogenation stage, and subjecting the residual aqueous layer to distillation to separate entrained small quantities of alcohol and nitrile therefrom.

9. Process for the manufacture of a primary lower alkyl mono amine by reacting a primary lower aliphatic monohydric alcohol containing more than one carbon atom per molecule with ammonia, comprising essentially i'lrst transforming the alcohol partially into nitrile by dehydrogenation in the vapor phase in a ilrst dehydrogenation stage in presence of a. dehydrogenation catalyst, employing an excess of ammonia over that theoretically necessary for conversion of the alcohol into nitrile, then subjecting the resultant mixture of nitrile and hydrogen to hydrogenation in the vapor phase in a second subsequent hydrogenation stage in the presence of a hydro-l genation catalyst, removing dissolved ammonia from the resultant amine-containing product, submitting the remaining liquid to distillation, drawing of! the amine as head product, separating the residual product into a nitrile-water mixture and an anhydrous mixture of secondary and tertiary amines and unconverted alcohol, removing the water from the nitrile-water mixture, returning the nitrile to the hydrogenation stage, and returning the anhydrous mixture to the dehydrogenation stage.

10. Process for the manufacture of monobutylamine comprising essentially subjecting butyl alcohol to dehydrogenation by the action of ammonia in the presence of nickel as a dehydrogenation catalyst at a temperature of about 300 C. in a first stage, employing an excess of ammonia over the amount theoretically necessary to convert the alcohol into the corresponding nitrile, and then effecting hydrogenation of the resultant nitrile by the action thereon of the resultant hydrogen in the presence of nickel as a hydrogenation catalyst at atemperature of about to about 100 C. in a second subsequent stage.

1l. Process for the manufacture of monobutylamine comprising essentially subjecting butyl alcohol to dehydrogenation by the action of ammonia in the presence of copper as a dehydrogenation catalyst at a temperature of about 360 C. in a first stage, employing an excess of ammonia over the amount theoretically necessary to convert the alcohol into the corresponding nitrile, and then effecting hydrogenation of the resultant nitrile by the action thereon of the resultant hydrogen in the presence of nickel as a hydrogenation catalyst at a temperature of about 90 C. in a second subsequent stage.

l2. Process for the manufacture of monoethylamine comprising essentially subjecting ethyl alcohol to dehydrogenation by the action of ammonia in the `presence of copper as a dehydrogenation catalyst at a temperature of about 340 C. in a rst stage, employing an excess of ammonia over the amount theoretically necessary to convert the alcohol into the corresponding nitrile, and then effecting hydrogenation oi' the resultant nitrile by the action thereon of the resultant hydrogen in the presence of copper as a hydrogenation catalyst at a temperature of about C. in a second subsequent stage.

HENRI MARTIN GUINOT. 65 

